All the previous files

obj.py

@@ -0,0 +1,30 @@
+import pyglet as p
+list_class=[]
+class meta_obj(type):
+    def __new__(cls,name,base,clsdict):
+        temp_class=type.__new__(cls,name,base,clsdict)
+        list_class.append(temp_class)
+        cls.priority_order=cls.depth=len(list_class) #by default, priority_order and depth depends on "when class was defined"
+        return temp_class
+
+class obj(p.sprite.Sprite):
+    __metaclass__=meta_obj
+    list_instance=[]
+    def __init__(self, *args, **kwargs):
+        super(PhysicalObject, self).__init__(*args, **kwargs)
+        list_instance.append(self)
+        self.velocity_x, self.velocity_y = 0.0, 0.0 # Velocity
+        self.list_update=[]
+
+    def update(self, dt):
+        """This method should be called every frame."""
+
+        # Update position according to velocity and time
+        self.x += self.velocity_x * dt
+        self.y += self.velocity_y * dt
+
+        for update_func in self.list_update:
+            update_func(dt)
+
+    def remove_update(self,update_func):
+        self.list_update.remove(update_func)